openInput

Returns a stream reading an existing file, with the
specified read buffer size. The particular Directory
implementation may ignore the buffer size. Currently
the only Directory implementations that respect this
parameter are FSDirectory and CompoundFileDirectory.

setLockFactory

Set the LockFactory that this Directory instance should
use for its locking implementation. Each * instance of
LockFactory should only be used for one directory (ie,
do not share a single instance across multiple
Directories).

getLockID

Return a string identifier that uniquely differentiates
this Directory instance from other Directory instances.
This ID should be the same if two Directory instances
(even in different JVMs and/or on different machines)
are considered "the same index". This is how locking
"scopes" to the right index.